Known dispenser tanks containing powdered reagent and having an orifice through which the powdered reagent may flow into a carrier gas conduit arranged to receive and to convey the powdered reagent to a point of use such as a pool of molten metal have a tendency to operate improperly due to the formation of lumps or globules of reagent or introduction of foreign matter particles which tend to interfere with or to close entirely the outlet orifice of the dispenser tank.
One known system in which a dispenser tank having a funnel shaped structure leading to an outlet orifice and having a cone shaped closure element is disclosed in U.S. patent application Ser. No. 142,648 filed Apr. 22, 1980.